1. Field of the Invention
This invention relates to thermoplastic welding.
In the field of thermoplastic welding, there are a number of known and accepted methods of performing the joining of polyolefin and other thermoplastics based products. One such product which requires joining, is polyolefin based pipes and fittings, for example.
2. Description of the Prior Art
To perform the operation of welding or joining, it is desirable for machines to be employed which are adapted so as to bring the two surfaces to be welded together with a equal distribution of pressure on the join area. To effect this equal distribution of pressure, existing machines incorporate a number of hydraulic pistons which are so positioned around the product, for example the pipe or fitting as to bring equal pressure to bear on the jointed surfaces.
There are a number of disadvantages to having the hydraulic pistons positioned as stated above. A machine of this type unfortunately offers poor accessability, having the pistons situated in close proximity to the component to be welded. This inhibits the versatility of the machine, making it difficult or even impossible to join awkward shaped fittings.
Another known machine in common use, incorporates only one piston, which is mounted in such a way that it moves a slidably mounted bracket, which in turn brings the surfaces of the component to be joined or welded together. The disadvantage of this method is that there is a tendency, (which increases with wear), that equal pressure is not applied to the surfaces of the join, leading to an inherent weakness in the join. These machines are prone to wear in regions which aggravates this problem. However, this machine does have the advantage of being very versatile, not having the disadvantage of inaccessability due to the pistons mentioned in the previous machine.